Proteolysis in Turkish White-brined cheese made with defined strains of Lactococcus

The effects of defined lactococcal starter strains (UC317, NCDO763, HP or SK11) on proteolysis in Turkish White-brined cheese were studied throughout ripening (1, 15, 30, 60 or 90 days). No significant differences were found in the gross compositions of the cheeses made with different strains, although the pH values were slightly different. Proteolysis was assessed at each ripening time by urea-polyacrylamide gel electrophoresis (urea-PAGE) of the pH 4.6-insoluble fractions and by reversed-phase high performance liquid chromatography (RP-HPLC) of the pH 4.6-soluble, the 70% (v/v) ethanol-soluble or 70% (v/v) ethanol-insoluble fractions of the cheese samples. Only minor differences were apparent during early ripening (at 1 or 15 days) but considerable differences were found in the urea-PAGE patterns after 60 days of ripening. Urea-PAGE of the pH 4.6-insoluble fraction of the cheeses showed that alpha(s1)-casein was hydrolysed more rapidly than beta-casein. The use of single strains of Lactococcus markedly influenced the peptide profiles obtained by RP-HPLC of the pH 4.6-soluble or 70% (v/v) ethanol-soluble or 70% (v/v) ethanol-insoluble fractions of the cheeses. Significant differences in the level of free amino acids were also observed between the cheeses; the cheeses made with NCDO763 or SK11 had the highest concentrations of free amino acids. The use of different lactococcal strains in the manufacture of Turkish White-brined cheese affected the degradation of alpha(s1)-casein, the formation of peptides detectable by RP-HPLC and the level of free amino acids. (C) 2004 Elsevier Ltd. All rights reserved.